Mill classifier

ABSTRACT

A mill classifier, particularly a roller mill classifier, has a strip rotor and a concentrically arranged guide vane ring with flow-optimized guide vanes and flow channels for a parallel incoming and outgoing flow without constriction or with widening and a diffuser effect. The flow-optimized guide vanes with an incident flow tube with vertical rotation axis and at least one guide plate are arranged adjustably for a tangential to radial incident flow of the strip rotor.

This application claims priority to PCT Application No. PCT/EP00/04637filed May 22, 2000, which claims the benefit of German Application No.199 61 837.2 filed Dec. 21, 1999.

The invention relates to a mill classifier, particularly a roller millclassifier according to the preamble of claim 1.

Roller mill classifiers, which can be arranged in integrated manner inor mounted on a roller and bowl mill or in a roller mill, e.g. in anair-swept mill, can be constructed as static or dynamic sifters orclassifiers. Combinations of a static and a dynamic classifier, which isthen referred to as a high effect classifier, are also known.

A high effect classifier is described in ZKG, vol. 46, 1993, No. 8, pp444 to 550, FIG. 7. The classifier has a cylindrical strip rotor and aconcentrically arranged guide flap or vane ring. The aim is to produce avery effective tangential flow between the static distributor and thestrip rotor, so that the coarse particles cannot reach the rotor. Thedisadvantages are an increased pressure loss and an increasing wear tothe guide vanes, particularly with high particle concentrations.

EP 204 412 B1 discloses a mill classifier, which has two superimposedguide vane rings. The guide vanes are adjustably arranged about verticalspindles, the guide vanes of the guide vane rings having independentlymounted spindles. Between the guide vane rings is provided a stationaryring and the adjusting devices are located at opposite ends of the guidevanes.

FR 2 642 994 A1 discloses a classifier with a strip rotor and aconcentrically arranged guide vane ring. In order to improveclassification the guide vanes of the guide vane ring are adjustableabout a vertical axis. The rotor strips are constructed in such a waythat in each case channels are formed with a cross-section widening fromthe outside to the inside, so that the centrifugal and resistance forcesacting on the particles of a predeterminable size, are in equilibriumover virtually the entire length of the channels. Thus, the equilibriumconditions are obtained via the profile of the rotor strips, the rotorspeed and the setting of the guide vanes for different separatingdiameters.

The cylindrical strip or rod basket rotor used in the afore-mentionedmill classifiers generally has a number of strips, which is at leasttwice as high as in so-called standard classifiers, which leads torelatively high manufacturing costs. The suspension and mounting of arod basket rotor also differs from the rotors of the standard classifierand contributes to higher manufacturing and assembly costs.

A known standard classifier is the LOESCHE centrifugal/basket classifierof the LKS design (ZKG, vol. 46, 1993, No. 8, p 446, FIG. 5). Thisdynamic classifier is constructed as a biconical or double cone striprotor and has a double cone rotor with screwed on classifying strips.The sloping rotor strips correspond to the incident flow from below andlead to a weak deflection of the grinding material-fluid flow. Inconjunction with a twisting flow caused by the setting of the blades ofa blade ring of the mill and a conically upwardly widening classifiercasing, a radial flow occurs at the strip rotor and increases frombottom to top and leading on the conically upwardly widening strip rotorto different centrifugal forces and to a relatively uniform classifyingover the entire strip length.

DE 44 23 815 C2 discloses a high effect classifier, in which a staticclassifying precedes a double cone rotor of a LOESCHE centrifugal/basketclassifier. By means of at least two axially superimposed and adjustablyarranged guide vane rings and a directional deflection of the grindingmaterial-fluid flow, part of the coarse material is separated, before adynamic reclassifying takes place through the following conical striprotor. The classifier has an improved separation efficiency and a lowerenergy consumption compared with standard classifiers, but does not inall cases meet the constantly increasing demands on efficiency and lowmanufacturing and maintenance costs.

The object of the invention is to provide a mill classifier,particularly a roller mill classifier, which in the case of particularlysimple construction has very low production costs and simultaneouslypermits a high flexibility and optimization of sifting or classifyingprocesses.

According to the invention the object is achieved by the features ofclaim 1. Appropriate and advantageous developments appear in thespecific description relative to the drawings and in the sub claims.

A fundamental idea of the invention is to retain the advantages of astrip rotor of a LOESCHE centrifugal/basket classifier and to achieve apurely dynamic classifying with the aid of at least one guide vane ring,the guide vanes and the rotor strips being so constructed and mutuallyoriented that the grinding material particles are not forced onto anorbit outside the strip rotor and are instead delivered into the striprotor.

According to the invention the guide vanes are shaped and positioned insuch a way that there is no so-called cyclone flow, but instead andwithout an upstream static classifying stage, a grinding material-fluidmixture is directly dynamically classified.

According to the invention a roller mill classifier with a strip rotorof a fundamentally known design and a guide vane ring arrangedconcentrically around the strip rotor is provided with flow-optimizedguide vanes, which are adjustable about a vertical rotation axis andforce a grinding material-fluid flow rising from the mill to atangential to radial incident flow of the rotor strips of the striprotor.

Preferably use is made of rotor strips, as are known in connection withLKS classifiers, but at least in the vicinity of the guide vanes arearranged vertically and therefore parallel to the guide vanes.

It is appropriate with respect to the production costs and efficientclassifying to use as the strip rotor a double cone rotor, particularlyof a LKS design LOESCHE centrifugal/basket classifier and to retool orreset the same in such a way that the known rotor strips are retained,but are perpendicular and no longer slope to a cylindrical rotor area.As the rotor strips have a radial dimensioning as with a LKS classifier,it is possible to significantly reduce the number of rotor stripscompared with the cylindrical rod basket rotors of the high effectclassifier. It has been found that the number of strips can beapproximately one third of that of a rod basket classifier and can bemax 50%.

A separation-efficient classifying without an upstream staticclassifying can be achieved by at least one guide vane ring with flowoptimized guide vanes, which have a rounded leading edge and at leastone guide plate and which are set with respect to the strip rotor insuch a way that an imaginary extension of the guide plates does notextend past the strip rotor and instead leads at least tangentially tothe outer edges of the rotor strips or radially into the rotor centre.

It is particularly advantageous to have guide vanes with a roundedleading edge and at least one guide plate located thereon in such a waythat roughly parallel or widening flow channels are formed between ineach case two guide vanes and the incoming and outgoing flows areapproximately the same.

In conjuncation with the rounded leading edge there is a parallel flowwithout constriction during the outgoing flow and as a result of aparticularly advantageous streamlined construction of the guide vanesthere is an expanding outgoing flow with a diffuser effect, which islinked with a recovery of pressure energy and therefore a reduction ofthe through-flow resistance of the classifier. However, in the case ofplanar guide vanes a flow channel with a nozzle effect is formed betweentwo guide vanes.

A cost-effective manufacture, assembly and simple adjustment of theflow-optimized guide vanes can be achieved in that the rounded leadingedge is constituted by a cylindrical or tubular incident flow body, e.g.an incident flow tube, on which the guide plate is arranged, e.g. weldedtangentially. It is also possible to indirectly fasten the guide plate,e.g. by means of an additional fastening plate to the incident flowtube. Whereas the fastening plate, which can be kept relatively narrow,can be fixed directly to the incident flow tube, the guide plate can bedetachably fixed, e.g. screwed to the fastening plate. Thus, if theguide plate wears, a relatively rapid, inexpensive replacement ispossible.

Appropriately the incident flow tube is circular cylindrical and madefrom an abrasion-resistant material, the rotation axis of the guidevanes being formed by the longitudinal axis of the incident flow tube.This leads to the advantage that both the mounting support for the guidevanes, e.g. by means of swivel pins, in the vicinity of the classifierhousing, and the adjustment from outside the classifier housing can beperformed in an extremely favourable manner.

Streamlined guide vanes are particularly advantageous for flow channelswith a diffuser effect and can e.g. be formed by two guide plates, whichare tangentially fixed to the incident flow body or tube. It isadvantageous for manufacture and mounting if both guide plates have asubstantially identical construction and engage on one another withrotor-side edge regions, i.e. taper off. However, the second plate canalso be narrower than the guide plate facing the classifying materialflow and can be fixed with a different setting angle to the guide platefacing the classifying material flow to the incident flow body, in orderto bring about an opening flow channel with diffuser effect.

It has been found that a separation-efficient classifying can beachieved with a strip rotor and at least one guide vane ring having anidentical number of rotor strips or guide vanes. In principle, the rotorstrips can have a Z-shaped construction.

An advantageous, flow-optimized form of the Z-shaped rotor strips can beachieved if the legs directed towards the guide vanes are rounded. As aresult of this rounded Z-shape there is a reduced resistance comparedwith the conventional angular shape. In addition, the flexural stiffnessof the rotor strips is increased, which is particularly advantageouswith an overhung arrangement.

In order to achieve a direct dynamic classifying over substantially theentire rotor area, the heights of the guide vanes and the rotor stripsare matched to one another. In the case of a strip rotor, whichcorresponds to a retooled double cone rotor of a LOESCHEcentrifugal/basket classifier, the cylindrical rotor area above aconical rotor area is to be dimensioned in such a way that the verticalrotor strips of the cylindrical rotor area have roughly the same heightas the concentrically arranged guide vanes of the guide vane ring. Theconical rotor area can be made hydraulically ineffective advantageouslyby means of a cover, e.g. a cover cone, which is located between thecylindrical and the conical rotor area. As the strip rotor with itsconical rotor area already functions within the oversize material returncone, there is no need to cover in a jacket-like manner said area or theconical strip ends.

Appropriately for the mill classifier according to the invention notonly are the rotor strips of the strip rotor constructed as for a LKS,but also the classifier housing, or at least its upper part, the bearingcollet, as well as the drive and driving shaft can be constructed as ina LOESCHE centrifugal/basket classifier. It is advantageous to omit thelower cone of the double cone rotor and to have a shortened constructionof the driving shaft. The classifier housing known from the LKSclassifier can be fundamentally adopted, but the space for the risinggrinding material fluid flow is constricted over the height of the guidevane ring, so that the particle flow is accelerated into the flowchannels of the guide vane ring.

The mill classifier according to the invention makes it possible tosupply the entire grinding material particles ranging from fine tocoarse material, to the strip rotor for a purely dynamic classifying.After passing through the grinding gap between the grinding rolls andthe grinding path, the particle flow is centrifuged into the fluid flow,flows upwards as a grinding material-fluid flow along the periphery ofthe grinding bowl and is transported through the guide vane ring,without prior separation of coarse particles, into the strip rotor. Thestrip rotor by centrifugal separation separates the coarse particlesfrom the overall particle flow, in that the coarse particles arecentrifuged by the strip rotor against the guide vane ends, where theydrop by gravity as oversize particles into the coarse material returncone.

It falls within the scope of the invention to provide more than oneguide vane ring over the height of the cylindrical rotor area of thestrip rotor and to equip the guide vanes of each guide vane ring with anadjusting device. It is advantageous to position a thrust ring below theguide vane ring.

It also falls within the scope of the invention, to use in place of aretooled rotor of a LOESCHE centrifugal/basket classifier, a rod basketclassifier of a high effect classifier and to provide same withconcentrically arranged, flow-optimized guide vanes according to thepresent invention.

Essential advantages of the mill classifier according to the inventionare relatively low manufacturing, assembly and installation costs due tothe possible retooling of a LKS. In addition, through the possibleretooling of a LKS, it is rapidly and inexpensively possible to complywith the wishes of customers for a separation-efficient, cost-effectivemill classifier.

The invention is described in greater detail hereinafter relative to theattached, highly diagrammatic drawings, wherein show:

FIG. 1 a mill classifier according to the invention with a guide vanering;

FIG. 2 a second variant of a mill classifier according to the inventionwith a guide vane ring;

FIG. 3 a detail of a strip rotor and on a larger scale guide vanes of aguide vane ring;

FIG. 4 a second variant of guide vanes;

FIG. 5 a highly diagrammatic representation of guide vanes and rotorstrips of a strip rotor according to FIGS. 1 and 2.

A mill classifier shown in FIGS. 1 and 2 is a roller mill classifier 2,which can be mounted on a roller mill. The roller mill is intimated bygrinding rolls 37 and a grinding path 39.

In a classifier housing 23 with an upper part 25, the roller millclassifier 2 has a dynamic classifier part 6 and a static guide vanering 4 for an upwardly flowing grinding material-fluid mixture 3. Thesupply of the feedstock to be ground takes place by means of a feed ordelivery tube 30, which is positioned laterally on the classifierhousing 23 and extends virtually to a discharge opening 33 of anoversize material cone 31, so that the feedstock together with theoversize material particles rejected by the dynamic classifier part 6,is supplied to a rotating grinding pan 39 and grinding rolls 37.

The dynamic classifier part 6 is constituted by a per se known striprotor 16 with a cylindrical rotor area 8 and a conical rotor area 18,which with respect to the number and construction, particularly withrespect to the radial width of the rotor strip 7 and a bearing collet24, a superimposed, not shown drive and a driving shaft 26,substantially corresponds to a double cone rotor of a LOESCHEcentrifugal/basket classifier. The conical rotor area 18 is renderedineffective by a facing, which is formed by a cover cone 28 inconjunction with the oversize material cone 31. Whereas in the upper,cylindrical rotor area 8 in conjunction with the flow-optimized guidevanes 5 of the guide vane ring 4 there is a purely dynamic classifying,the sloping classifying strips of the conical rotor area 18 ensure themechanical connection to the double cone rotor 35.

In principle, the classifier housing 23 and the upper part 25 of saidhousing 23 have been taken from the LOESCHE centrifugal/basketclassifier, i.e. a standard classifier, but the classifier housing 23 inthe vicinity of the cylindrical rotor area 8 is tapered or narrowedupwards and a “retracted” housing shape 38 is obtained.

With regards to the classifier housing 23, the mill classifier 2 shownin FIG. 2 corresponds with the exception of the retracted housing shape38 and with respect to the classifier housing upper part 25, bearingcollet 24 and driving shaft 26, as regards both shape and radialextension of the rotor strip 7 to the known LKS standard classifier, butunlike in the classifier according to FIG. 1 has no conical rotor area18, but instead only a cylindrical rotor area 8 with vertical rotorstrip 7 in the narrowing housing 38. There is no longer a double cone 35as in the case of the mill classifier 2 according to FIG. 1. Coincidingfeatures of the mill classifier 2 according to FIGS. 1 and 2 are givenidentical reference numerals.

The guide vane ring 4 of the mill classifier 2 in FIGS. 1 and 2 isprovided with flow-optimized guide vanes 5, which can be adjusted abouta vertical rotation axis 9 (cf. FIGS. 3 to 5). In order to achieve adynamic classifying of the grinding material-fluid mixture 3 and aseparation into coarse material 32 and fine material 34 by rejection atthe rotor strip 7 of the strip rotor 16, the guide vanes 5 are BOconstructed and arranged that there is no centrifugal flow in aclassifying area 20 between the strip rotor 16 and the guide vane ring4, but instead there is a tangential to radial incident flow of thestrip rotor 16 (cf. FIGS. 3 and 5).

FIGS. 3 to 5 shown in exemplified manner flow-optimized guide vanes 5 ofthe guide vane ring 4. In a first variant in FIG. 3, the guide vanes 5shown larger than the rotor strip 7 are provided with a rounded leadingedge 10 and a guide plate 11, which is fixed directly and tangentiallyto the rounded leading edge 10. Such guide vanes 5 are shown in FIG. 3as lower guide vanes, whereas the two upper guide vanes 5 have astreamlined construction and besides the guide plate 11, which faces thegrinding material-fluid mixture 3 or the classifying material flow, alsohas a plate 12, the plate 12, which is remote from the classifyingmaterial flow, is also tangentially fixed to the rounded leading edge10, which is advantageously a circular incident flow tube.

In order to bring about an opening flow channel 13 between two guidevanes 5, the second plate 12 can be fixed with a different setting angleto the guide plate 11 to the leading edge 10. The guide plate 11 andplate 12 of the two upper streamlined guide vanes 5 in FIG. 3 have asubstantially identical construction and engage with one another withrotor-side edge areas 21, 22 and therefore taper off. However,streamlined guide vanes 5 are not restricted to this variant.

FIG. 4 shows alternatively constructed guide vanes 5 with an incidentflow tube 10, a vertical rotation axis 9 on the longitudinal axis of theincident flow tube 10, with a guide plate 11 and a plate 12. Unlike theguide vanes 5 shown in FIG. 3, the guide plate 11 is not directly fixedto the incident flow tube 10, but is instead detachably fastened theretoby means of an additional fastening plate 17. In this way thewear-exposed guide plate 11 can be replaced. Appropriately both theguide plate 11 and the incident flow tube 10 are made from anabrasion-resistant material or at least partly are provided with anabrasion-resistant coating and/or surface structure. Plate 12 and/or theadditional fastening plate 17 can also be given an abrasion-resistantconstruction. FIG. 4 makes it clear that the setting angle of theindirectly fastened guide plate 11 and/or the plate 12 can be made thesame or different, so that either parallel or widening flow channels 13can be formed and a classifying in accordance with requirements can beobtained.

FIG. 5 shows in exemplified manner two rotor strips 7 of a strip rotor16. The rotor strips 7 fundamentally have a Z-shaped construction, butat the end thereof facing the guide flap ring 4 have a rounded leg 27,which leads to a reduced resistance and to a higher flexural stiffness.The guide vanes 5 shown in FIG. 5 have as the rounded leading edge 10and incident flow tube, whose vertical axis forms the rotation axis 9 ofthe guide vanes 5. The guide vanes 5 are provided with a guide plate 11,which is held indirectly, namely by means of fastening devices, e.g.fastening plates 17, on the incident flow tube 10. Whereas the fasteningplates 17 shown in FIG. 4 are angled, for the guide vanes 5 according toFIG. 5 planar fastening plates 17 are used, which are fastened, e.g.welded tangentially to the incident flow tube 10.

The setting of the guide vane ring 4 with respect to the rotor strips 7provided for the purely dynamic classifying on the part of the millclassifier 2 can be gathered from FIGS. 3 and 5. The guide vanes 5 withguide plates 11 directly or indirectly fastened to the incident flowtube 10 or the streamlined guide vanes 5, e.g. with a guide plate 11 anda plate 12, are so oriented that their imaginary extensions, shown incontinuous line form, do not lead past the strip rotor 16 and insteadlead tangentially to the outer edges of the rotor strips 7 to radiallyin the direction of the centre of the strip rotor 16.

In FIGS. 3 and 5 the guide vanes 5 are set at an angle of approximately60°, so that there is an incident flow of the radially oriented rotorstrips 7 and a rejection or repulsion of coarse material particles 32,whereas the fine material particles pass into the strip rotor 16. FIG. 5shows at the lower guide vane 5 that the coarse material particles 32are centrifuged towards the guide vane 5 by the Z-shaped rotor strips 7and in said flow-minimized area drop downwards into the coarse materialcone 31 (cf. FIGS. 1 and 2). FIG. 3 and in particular FIG. 5 alsoillustrate the construction of roughly parallel flow channels 13 with anapproximately identical incoming flow 14 and outgoing flow 15 as aresult of the flow-optimized guide vanes 5 with guide plates 11 andincident flow body 10. Necessarily in the case of guide vanes without anincident flow body or bodies there is necessarily narrowing flowchannels with a nozzle effect during outflow and this is shown by brokenlines in FIG. 5. In the parallel flow channels 13 or also in thewidening flow channels, where there is an advantageous diffuser effectand a recovery of pressure energy, all the particles of the grindingmaterial-fluid flow from the roller mill, i.e. fine to coarse material,are transported into the strip rotor without prior coarse particles 32are separated from the rotor 16 by centrifugal separation, in that theyare centrifuged against the guide vanes 5, i.e. against the armouredguide plates 11 or plates 12 (cf. FIGS. 3 to 5). By gravity the coarsematerial particles 32 in the classifying area 20 drop as oversizematerial into the oversize material cone 31 and are returned to thegrinding path.

What is claimed is:
 1. A roller mill classifier, comprising: a guidevane ring for a rising grinding material-fluid flow, wherein the guidevane ring includes guide vanes that are adjustable about verticalrotation axes; a dynamic classifier part comprising a strip rotor havinga cylindrical rotor area and rotor strips that are concentricallysurrounded by the guide vanes; a classifying area, formed in thecylindrical rotor area; wherein the guide vanes of the guide vane ringhave a flow-optimized shape having a rounded leading edge and at leastone guide plate; wherein the guide vanes are adjustable between adirection tangential and a direction radial to the cylindrical rotorarea; wherein the strip rotor comprises a double cone rotor of acentrifugal classifier having inclined rotor strips in a lower cone andbeing retooled such that the rotor strips are vertically arranged to acylindrical rotor area; and wherein the strip rotor includes a conicalrotor area that is made hydraulically ineffective.
 2. A roller millclassifier, comprising: a guide vane ring for a rising grindingmaterial-fluid flow, wherein the guide vane ring includes guide vanesthat are adjustable about vertical rotation axes; a dynamic classifierpart comprising a strip rotor having rotor strips that areconcentrically surrounded by the guide vanes; wherein the guide vanering and the dynamic classifier part form a classifying area; whereinthe strip rotor is at least zonally cylindrically constructed andincludes a cylindrical rotor area having vertical rotor strips; whereinthe guide vanes of the guide vane ring comprise a flow-optimized shapeand are adjustable between a tangential and radial incident flow of thecylindrical rotor area; wherein the guide vanes include a roundedleading edge and at least one guide plate; wherein the vertical rotationaxis of each guide vane is formed in the rounded leading edge; andwherein a first guide vane and an adjacent guide vane form a flowchannel having a diffuser effect that comprises at least one of aparallel flow channel and a widening flow channel.
 3. The millclassifier of claim 2 wherein a fist guide vane and an adjacent guidevane form a flow channel having a diffuser effect, the flow channelbeing one of substantially parallel and widening.
 4. The mill classifierof claim 3, wherein the rounded leading edge of each guide vanecomprises an incident flow body that includes an incident flow tube, andwherein the guide plate is arranged directly and tangentially at theincident flow tube.
 5. The mill classifier of claim 4, wherein the guideplate is attached to the incident flow tube using a fastening plate. 6.The mill classifier of claim 4, wherein the incident flow tube comprisesa circular cylindrical construction, and wherein the rotation axis ofeach guide vane is formed by the longitudinal axis of the incident flowtube.
 7. The mill classifier of claim 4, wherein the guide vanescomprise a streamlined construction, and wherein a further plate isarranged tangentially to the incident flow tube.
 8. The mill classifierof claim 7, wherein the further plate is substantially similar to theguide plate.
 9. The mill classifier of claim 7, wherein the flow channelwidens, and wherein the fixer plate is located at the incident flow tubeand has a different setting angle than the guide plate.
 10. The millclassifier of claim 7, wherein the guide plate and the further platenearly engage rotor-side edge areas.
 11. The mill classifier of claim 2,wherein a guide plate that faces coarse material particles from thedynamic classifier part at least partially comprises one of awear-resistant material and a wear-resistant coating.
 12. The millclassifier of claim 2, wherein the rotor strips comprise a z-shapedconstruction, and wherein a guide vane side of each rotor strip has arounded leg.
 13. The mill classifier of claim 2, wherein the strip rotorcomprises a double cone rotor of a centrifugal classifier havinginclined rotor strips in a lower cone and being retooled such that therotor strips are vertically arranged to the cylindrical rotor area, andwherein the strip rotor includes a conical rotor area that is madehydraulically ineffective.
 14. The mill classifier of claim 13, whereinthe double cone rotor includes rotor strips that are substantiallyvertical above the conical rotor area and form the cylindrical rotorarea, and wherein the conical rotor area is covered by a cover cone. 15.The mill classifier of claim 13, wherein the rotor strips of thecylindrical rotor area and for a cylindrical envelope coaxial to theguide vane ring, have a height corresponding to a height of the guidevanes of the static classifier.
 16. The mill classifier of claim 13,wherein the classifier comprises: a classifier housing upper part; abearing collet; a drive positioned above the bearing collet; a drivingshaft; and a classifier housing conically tapering over a height of theguide vane ring.
 17. The mill classifier of claim 2, wherein the striprotor comprises a rod basket classifier rotor having vertical rotorstrips.
 18. A roller mill classifier, comprising: a guide vane ring fora rising grinding material-fluid flow, wherein the guide vane ringincludes guide vanes that are adjustable about vertical rotation axes; adynamic classifier part comprising a strip rotor having a cylindricalrotor area and rotor strips that are concentrically surrounded by theguide vanes; a classifying area, formed in the cylindrical rotor area;wherein the guide vanes of the guide vane ring have a flow-optimizedshape having a rounded leading edge and at least one guide plate;wherein the guide vanes are adjustable between a direction tangentialand a direction radial to the cylindrical rotor area; wherein the rotorstrips comprise a z-shaped construction; and wherein a guide vane sideof each rotor strip has a rounded leg.
 19. The mill classifier of claim18, wherein the guide vanes have a rotation axis that is formed in thevicinity of the rounded leading edge, and wherein a first guide vane andan adjacent guide vane form a flow channel having a diffuser effect, theflow channel being one of substantially parallel and widening.
 20. Themill classifier of claim 18, wherein the strip rotor comprises a doublecone rotor of a centrifugal classifier having inclined rotor strips in alower cone and being retooled such that the rotor strips are verticallyarranged to a cylindrical rotor area, and wherein the strip rotorincludes a conical rotor area that is made hydraulically ineffective.